Summary: This layer was created to depict industrial land areas present in 1968. The layer is intended to contribute to a larger mapping and modeling effort designed to spatially depict land areas that may be sources of Polychlorinated Biphenyls (PCBs) or mercury in the San Francisco Bay Area. The land areas are termed “old industrial” due to their presence prior to roughly 1970, the timeframe when PCB production in the U.S. ceased. Old industrial land parcels in Alameda, Contra Costa, San Mateo, Santa Clara and Solano counties are depicted. Parcels in the datalayer are defined via the most currently available assessor’s parcel data for each county.